The invention relates to a method of forming a contact plug in a semiconductor device and, more particularly, relates to a method of forming a contact plug in a semiconductor device being capable of forming a contact plug through a self align contact (SAC) process.
A flash memory device is a non-volatile memory device which can store data when electric power is interrupted. The flash memory device is characterized in that electrical program/erase operations can be performed and a refresh function for rewriting the data is not required. Such flash memory devices are classified as NOR flash memory devices and NAND flash memory devices according to the structure of the cell and an operation condition. In the NOR flash memory device, a plurality of word lines are connected to each other in parallel so that program and erase operations for the optional address can be performed, and so the NOR flash memory device is mainly employed in application fields requiring high operation speed. On the other hand, the NAND flash memory device has a structure in which a plurality of memory cell transistors are connected to each other in series to form one string and one string is connected to a source and a drain, such NAND flash memory devices are mainly employed in the high integrated data storage application field.
As memory devices become more highly integrated and microminiaturized, a process margin is reduced so that it is gradually difficult to form a source/drain contact plug connecting a semiconductor substrate on which source/drain regions are formed and a metal wire,